The invention relates to a fluid-cooled fuel cell, in which the cell surfaces are supplied with reaction media via axial supply ducts and radial distribution ducts.
Patent application 44 42285.7 (94 P 3704), which has not yet been published, describes a battery that comprises fuel cells and in which the cell surfaces are also supplied via axial supply ducts and radial distribution ducts. However, this design is primarily suitable for fuel cells which are cooled via direct air cooling, since neither distribution ducts nor supply ducts for coolant are provided. Batteries comprising fuel cells have to be cooled more intensively as the power density per unit area of the battery increases. In many cases, pure air cooling is not sufficient, because of its limited heat transfer. Fluid cooling would therefore be necessary, but in the case of fuel cells of this type it is possible only by replacing the cooling medium air with a fluid, which is guided in an external vessel which encloses the entire battery. The problem here is, on the one hand, that the fluid may come into direct contact with the electrolyte (which leads to creepage currents and to corrosion) and, on the other hand, that the container takes up space. Practical fluid cooling is therefore not yet available for this design.
Although DE 42 34 093 discloses the corrosion-free cooling of cell surfaces of a fuel cell using a liquid, it does not disclose any design which ensures uniform inflow to the surfaces which are to be cooled and those which are active. Instead, in this prior art, the result of a point-like inlet is a diagonal flow of the media over the cell surfaces, which is accompanied by an undersupply to those marginal regions of the cell surface that are adjacent neither to an inlet opening nor to an outlet opening. As a result, the performance of the fuel cell is reduced by comparison with a uniform supply to the surfaces. Furthermore, the constructional elements that are disclosed in that document require high production costs, since the individual supply and distribution ducts have to be terminated in a gastight manner by means of one or more collecting lines. Both the high production costs and the partial undersupply to the cell surface have a detrimental effect on the attractiveness of the fuel cell as one of the energy converters of the future.